Russell-Silver syndrome is a rare disease and is characterized by growth retardation with antenatal onset, characteristic facies and limb asymmetry. One major clinical characteristic is relative macrocephaly. The incidence is evaluated at 1-30/100 000 cases and about 400 cases have been reported in the literature. It was first clinically described by Russel and Silver et al. in 1953/54 independently (Russel 1954; Silver et al. 1953). The clinical picture of RSS is heterogenous. Weight is often more affected than size, with little subcutaneous fat tissue. Bone maturation is delayed, in accordance with small stature. The fontanelle may be late to close. The skull has a normal circumference, which may contrast with the rest of the body and confers a pseudohydrocephalic appearance. The wide prominent forehead contrasts with the small, triangular face with a small pointed chin, a wide mouth with thin lips and down-turned corners, large eyes and bluish sclera. Lateral and usually partial asymmetry of the limbs is observed in 60% to 80% of cases, but is not progressive. Shortness and/or clinodactyly of the fifth fingers is a common finding. Patients may be slow to learn motor skills, and in rare cases, may be mildly intellectually deficient. They may have feeding difficulties and hypoglycaemia (Toutain 2007; Price et al. 1999).

The genetic aetiology of RSS is only partly understood. About 10% of RSS patients have maternal uniparental disomy (mUPD) for chromosome 7 and up to 50% have methylation defects in the imprinted domain on chromosome 11p15 (Abu-Amero et al. 2008).